Cell and protein mechanics has applications ranging from cellular development to tissue engineering. Techniques such as magnetic tweezers, optic tweezers and atomic force microscopy have been used to measure cell deformation forces of the order of piconewtons to nanonewtons. In this study, an array of polymeric polydimethylsiloxane (PDMS) microbeams with diameters of 10–40 µm and lengths of 118 µm was fabricated from Sylgard® with curing agent concentrations ranging from 5% to 20%. The resulting spring constants were 100–300 nN µm−1. The elastic modulus of PDMS was determined experimentally at different curing agent concentrations and found to be 346 kPa to 704 kPa in a millimeter-scale array and ∼1 MPa in a microbeam array. Additionally, the microbeam array was used to print laminin for the purpose of cell adhesion. Linear and nonlinear finite element analyses are presented and compared to the closed-from solution. The highly compliant, transparent, biocompatible PDMS may offer a method for more rapid throughput in cell and protein mechanics force measurement experiments with sensitivities necessary for highly compliant structures such as axons.

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Current and predicted climate changes caused by global warming compel greater understanding of the molecular mechanisms that plants use to survive drought. The desiccation-tolerant fern Polypodium polypodioides exhibits extensive cell wall folding when dried to less than 15% relative water content (RWC) and rapidly (within 24 h) rehydrates when exposed to water and high humidity. A 31-kDa putative dehydrin polypeptide expressed in partially and fully dry tissues detected via western blotting was present only during drying and rapidly dissipated (within 24 h) upon tissue rehydration. Immunostaining indicates the presence of dehydrin near the cell wall of partially and fully dried tissues. Atomic force microscopy of tracheal scalariform perforations indicates that dry vascular tissue does not undergo significant strain. Additionally, environmental scanning electron microscopy reveals differential hydrophilicity between the abaxial and adaxial leaf surfaces as well as large, reversible deformation. The ability to avoid cell wall damage in some desiccation-tolerant species may be partially attributed to cell wall localization of dehydrins enabling reversible, large cell-wall deformation. Thus, the de novo synthesis of dehydrin proteins and potential localization to the cell walls of these desiccation-tolerant species may play a role in avoiding mechanical failure during drought.

Some fundamental issues concerning the design and performance of stochastic porous structures are examined, stemming from application of advanced fibrous electrode substrates in NiMH automotive cells. These electrodes must resist corrosion and local failures under hundreds of charge/discharge cycles. Such fibrous materials can be effectively used as substrates for chemical reactions because of their combinations of high surface area and high conductivity. Key questions concerning the relationships among connectivity and conductivity, scale and variability in material response are addressed. Two techniques are developed and compared for use in predicting these materials’ conductivity. The first approach uses a statistical technique in conjunction with an adaptation of classic micromechanical models. The second approach uses the statistical generation technique, followed by an exact calculation of 2D network conductivity. The two techniques are compared with one another and with classic results. Several important conclusions about the design of these materials are presented, including the importance of use of fibers with aspect ratios greater than at least 50, the weak effect of moderate alignment for unidirectional conductivity, and the weak power-law behavior of conductivity versus volume fraction over the range of possible behaviors.

The best means we have found to reduce raw AFM data is to measure several diameters with a single scan, using valley-to-valley measurements. Structural, fibrillar collagens of the nerve and tendon become larger in rats exposed to prolonged diabetes.